Electrical time modulated pulse communication system



D. D. GRIEG July 4, 1950 ELECTRICAL TIME MCDULATED PULSE COMMUNICATIONSYSTEM Filed Sept. l, 1945 4 Sheets-Sheet l I N V EN TOR. 00A/4L D D.GW/EG ATTORNEY D. D. GRIEG 2,513,308

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ELECTRICAL TIME MODULATED PULSE COMMUNICATION SYSTEM July 4, 1950 D. D.GRIEG .2,513,308

ELECTRICAL TIME MODULATED PULSE COMMUNICATION SYSTEM Filed Sept. l, 19454 Sheets-Sheet 4 DOA/ALD D. GP/EG TTIPNEY Patented July 4, 1950ELECTRICAL TIME MODULATED PULSE COMMUNICATION SYSTEM Donald D. Grieg,Forest Hills, N. Y., assgnor to Federal Telephone and Radio Corporation,New York, N. Y., a corporation of Delaware Application September 1,1945, Serial No. 614,079

6 Claims.

This invention relates to a communication system for transmitting andreceiving two separate signals on each p ulse of a single signalmodulated pulse wave. More particularly it deals with the method and themeans for producing such a wave from a base wave and two separatesources of signal energy.

It is an object of this invention to produce a wave carrying a train ofpulses wherein each pulse carries two separate signals in an efcient,economic and eiective manner.

Another object is to transmit and receive such a signal modulated pulsewave.

Another object is to demodulate such a pulse wave into the two separatesignals modulated thereon.

Another object is to modulate two signals on one pulse wave, wherein onesignal is modulated on the leading edge of the pulse and another signalis modulated on the trailing edge of each pulse.

Another object of this invention is to provide a system forcommunicating two separate signals on a single time modulated pulsewhereby crosstalk between the two signals is avoided when they aredemodulated.

Still other objects and features of this invention will appear from timeto time in the description which follows:

The system of this invention includes a. source of a simple base wavesuch as a sine wave, a constant frequency pulse wave, a saw-tooth wave,or the like, and two sources of signal energy, such as audio signals.From this base wave are produced two pulse trains, each of which is timemodulated according to one of the sources of signal energy. Thisfunction may be carried out by rst shaping, delaying and/or changing thephase of the base wave and then modulating the resulting wave or wavesaccording to the signals, such as by a modulating clipping device. Thetwo resulting modulated waves are then interleaved or mixed to form anew pulse wave wherein the pulses of each separate modulated wave areout-of-phase with each other and two adjacent pulses (one from eachmodulated wave) are joined to form a single pulse. This combined wavemay be produced by a mixer, a mixer and a trigger circuit, or anothersuitable combining device so that each pulse of the final wave will haveone time modulated signal on its leading edge and another time modulatedsignal on its trailing edge. The resulting wave may then be transmitted,received, and demodulated. The demodulating means comprises a means forseparating the leading and trailing edge of each pulse of the receivedwave such as by a differentiating circuit and then time demodulatingeach of the resulting separated pulse waves to reproduce the originalsignals.

These and other features and objects of this invention will become moreapparent upon consideration of the following detailed description of thefollowing embodiments to be read in connection with the accompanyingdrawings in which:

Fig. 1 is a schematic wiring diagram, partially in block, of one form ofa circuit for producing the time modulated pulse wave of this invention;

Fig. 2 is a graph illustrative of the different wave forms produced inthe system disclosed in Fig. l;

Fig. 3 is a schematic wiring diagram partially in block, of another formof a circuit for producing the time modulatedpulse wave of thisinvention;

Fig. 4 is a graph illustrative of the different wave forms produced inthe system disclosed in Fig. 3;

Fig. 5 is a schematic wiring diagram, partially in block, of ademodulating circuit for the pulse waves produced by the system shown inFig. 1 or Fig. 3; and

Fig. 6 is a graph illustrative ofthe different wave forms produced inthe system shown in Fig. 5.

Referring now to Figs. 1 and 2 of the drawings, there is shown a circuitcomprising a base wave generator l, such as a sine wave generator, andtwo separate sources of signal energy 2 and 3 hereinabove called signalA and signal 13. The sine wave l, (Fig. 2) from the generator l, ismodulated in the modulator clipper 5 to produce a train of pulses, suchas that shown at li (Fig. 2). The modulator clipper 5 may be any one ofknown forms of` gate clipper clipping between two levels and may be ofthe double diode type. .applied signal which varies the bias on thediodes of the clipper. Both the leading and trailing edges of the pulsewave t are time modulated according to the same signal A. This wave isthen diierentiated in the diiierentiator clipper l to produce a wave 8which is then clipped along the level 9 so that only the leading edgepulses Il) from wave 6 pass from the clipper l through line l I andcondenser I2 to the mixer lt. Thecircuits of the blocks 5 and 'l may bethe same as corresponding blocks shown in de- The clipping levels areshifted by the tail for the channel of signal B the description of whichnow follows.

In order to produce a similar train of pulses modulated according tosignal B from the same sine wave 4, sine wave d is passed through branchline IG to the phase shifter i5 comprising condenser I 5 and variableresistor I1 to delay sine wave 5 to produce the wave i8, shown dotted inFig. 2. This delayed sine wave is passed to the modulator clipper I9,similar to that of 5 which may comprise a, double diode to produce ladouble constant width clipping at levels 2i, which levels vary from lessto more positive positions between the limits 22 in accordance with thesignal B connected through trans-- former 23. The variable resistances25 and determine the width between the clipping levels 2l. Since theclipping levels 2l vary vertically along the sloping portion of the waveiS, the leading and trailing edges of the pulses of resulting clippedwave 2 are horizontally or time modulated within the limits 213.Similarly as in the pulse train of signal A, both the leading and thetrailing edges of pulses in wave 2l are time modulated toward and awayfrom each other according to the energy in signal B Wave 2'! then passesfrom the clipper modulator l5 through line 29 to the diierentiator andamplifier clipper network 3G similar to that of l. The diierentiatorcircuit comprises condenser 3i and resistance 32, which produces thewave consisting of a series of positive pulses 3e corresponding to theleading edges of the pulses of wave 2l, and a series of negative pulsescorresponding to the trailing edges of the pulses in wave 2l. Theamplier clipper tube 5f! is biased by the C- connected to the resistor32 so as to clip the wave 33 along the level 35 to produce a waveconsisting only of the positive pulses 3S. Pulses 35 then pass fromplate 3l of the tube (ifi to the mixer I3 through line 33.

In order to prevent the pulse waves from the clipper 'I from feedingback into the clipper and vice versa lines l2 and 3@ are connected tothe grids of triodes 49 and il respectively, 'rom which a, new wave 39,Fig. 2, is withdrawn over line 42.

To convert pulses l0 and 36 into the wider pulse of the wave d3, theyare passed through a trigger circuit shown at 14 which may comprise twotriodes 115 and d@ connected in such a manner so that when pulse 36 istransmitted to the grid of triode (S5 it will cut out the triode E5 andfire tube which will continue to pass current until the second pulse Il)passes and then tube l5 will be cut out and tube d6 will fire and thecurrent will be reversed through the two tubes thereby forming one pulselil from the two separate pulses l0 and 36. The trigger circuit lli maybe any suitable form of counting or commutating arrangement includingtwo tubes, such as in the form of a multivibrator having two amplitudelevels at which it is stable and which multivibrator is tripped from onelevel to a second level by the rst incoming pulse and return to theorginal level by the second pulse. Since pulses ii.) and 35 are eachseparately time modulated, two separate signals A and B are representedby the edges i8 and 149 of the pulse 41. The wave 43 collected from theplates of the tubes 45 and 45 is then passed through line to a suitabletransmitter, such as an ultra high frequency transmitter, fortransmission of the resulting pulse wave G3 to any desired sources suchas over a high frequency cable or a given radio frequency.

Another circuit for producing a wave similar to wave 43 is shown in Fig.3. Referring to Figs. 3 and 4 a pulse generator 5| may be employed toproduce a wave having the form shown at 52 in Fig. 4. This wave is thenshaped so that signals A and B may be applied to energy thereof, toproduce the desired pulse modulated wave.

For signal A the Wave is passed through wave shaper 53 comprising thetriode 54 and condenser 55 wherein the shape of the wave which iswithdrawn through line 55 is like that shown at 51 in Fig. 4, having asloping edge 58 for each pulse. This wave may be amplified if desiredand passed through a modulator clipper 59, similar to that described at30 in Fig. 1, to produce a Wave 6l] in which the leading edge of eachpulse is time modulated according to the signal "A, introduced into thetime modulator 59 at 6|.

In order to produce a similar pulse wave in which the trailing edge istime modulated according to the energy in signal 13, the originalpulse'wave 52 is passed through a delay device 'S2 which may comprise anetwork of inductances of capacitances to assimulate a transmissionline4 The delayed wave then is passed into phase inverter 63 comprisinga triode 64 for inverting the delayed pulse Wave 52 to form the wave 65withdrawn from the plate of tube 64. Wave 65 is now passed through line66 to a diierentiator clipper 6l, which may comprise a condenser 68,resistor 69 and an amplifying tube l0, similar to that shown indiierentiator clipper 3U in Fig. l, but having different impedancevalues so that the wave entering the grid of the tube 'I0 yfrom thediilerentiator will have the form 'H shown in Fig. 4, and may be clippedalong line T2 to separate the positive pulses having sloping trailingedges "d3, complementary to edges 58 ofy wave ii?. Since tube It invertsthe wave 12 the output from 'i2 is then passed thru another phaseinverter 53a similar to 53. These resulting positive pulses from phaseinverter '63a are time modulated in the clipper modulator la, similar tothat shown in 59, but with a phase inverter added by the signal Bintroduced at 75. From the modulator clipper M is withdrawn the pulse'train l@ having the trailing edge of eachY pulse time modulated inaccordance with the signal energy 13.

The two time modulated pulse trains 60 and 16 are now passed into themixer Tl, similar to the mixer I3 in Fig. 1, wherein the new puls'evwave'iii is produced having the leading edge of each pulse modulatedaccording to signal A and the trailing edge of the pulse time modulatoraccording to signal 13. It should be noted that the trailing edge ofeach pulse of wave train 66 and the leading edge of each pulse of wavetrain 76, are in phase with each other so that there is substantially noreproduceable pulse occurring in the center of each pulse produced inWave 18. However, if another pulse does occur at the center of eachpulse on wave 18 due to inadvertent over or underlap of the pulses 60and 16, it may easily be removed by a passing of the wave 18 through asuitable lter or limiter before it is applied to a transmitter. Bothpulse waves 43 and 'l8`are substantially the same form.

Referring now to Figs. 5 and 6 the transmitted pulse waves #i3 or 78 arereceived over line 19 and passed through a differentiating networkcomprising a condenser and resistor similar to that previouslydescribed. For convenience wave form 43 or 18 is reproduced as wave form8| in Fig. 6, which after being differentiated has the form 82, whereinthe leading edges of each pulse 83 of wave 8| form positive pulses 84and the trailing edges of each pulse 83 thereof form negative pulses 85.Wave 82 then is passed through a suitable clipper 86 which clips thewave 82 along the line 81 to produce a series of positive pulses 84which are passed to a suitable pulse time demodulator 88 from which thesignal A is again reproduced and withdrawn through line 89.

For signal B," the differentiated wave 82 is also passed through a phaseinverter 90, similar to that of 63 shown in Fig. 3, from which wave 9|is withdrawn and passed into clipper 92, similar to 86, wherein thepositive pulses (which correspond to the trailing edges of the pulses 83of wave 8|) are removed by clipping along the level 93. The clipped wave9| then is passed'to a pulse time demodulator such as shown at 94 anddisclosed in copending application, Ser. No. 459,959, led September 28,1942, now Patent No. 2,416,306, granted February 25, 1947. This pulsetime demodulator may comprise a harmonic sine wave generator 95 whichproduces the wave 96 (Fig. 6) upon which the positive pulses 9`| of wave9| are superimposed. The resulting composite wave having pulses spacedat diierent positions along the sloping edges of the sine wave 96, ispassed through the low pass filter 99 from which the audio signal B iswithdrawn through line |00. The audio signal B has the form of thedotted wave shown in Fig. 6. Signal wave A is similarly shown in Fig. 6by dotted wave |02.

From the above description it can be seen that a single pulse may carrytwo separate signals one time modulated on its leading edge and theother time modulated on its trailing edge.

While the principles of the invention have been described in connectionwith specic apparatus it is to be clearly understood that thisdescription is made only by way of example and not as a limitation onthe scope of the invention as defined in the objects and theaccompanying claims.

I claim:

1. A system for producing a pulse wave carrying one time modulatedsignal on the leading edge of each pulse and a different time modulatedsignal on the trailing edge of each pulse, comprising: a base wavesource, two sources of different signal energy, means to change thephase of said base wave, means to produce two pulse trains one from theoriginal base wave and another from the base wave out of phase with theoriginal base wave, means for respectively time modulating the pulses ofsaid trains with energy from said signal sources, means to interleavethe pulses of said pulse trains to produce a new pulse wave, and triggercircuit means to combine successive pairs of pulses in said new pulsewave to form a series of single pulses, each bearing two signals.

2. A system for producing a pulse wave carrying one time modulatedsignal on the leading edge of each pulse and a different time modulatedsignal on the trailing edge of each pulse, comprising: a base wavesource, two sources of different signal energy, means to change thephase of said base wave, means to produce two pulse trains one from theoriginal base wave and another from the base wave out of phase with theoriginal base wave, the means to produce one of said pulse trainsincluding a differentiating means and a clipping means, means forrespectively time modulating the pulses of said trains with energy fromsaid signal sources, means to interleave the pulses of said pulse trainsto produce a new pulse wave, and means to combine successive pairs ofpulses in said new pulse wave to form a series of single pulses, eachbearing two signals.

3. A system for producing a pulse Wave carrying one time modulatedsignal on the leading edge of each pulse and a diierent time modulatedsignal on the trailing edge of each pulse, comprising: two sources ofsignal energy, means to produce two pulse trains respectively timemodulated at one edge per pulse with energy from said signal sources,means controlling said pulse trains so that the unmodulated edges ofcorresponding pulses of said pulse trains coincide and means to combinecorresponding pulses, one from each train, into a single pulse of thedesired pulse wave.

4. The system for producing a pulse wave carrying one time modulatedsignal on the leading edge of each pulse and a diierent time modulatedsignal on the trailing edge of each pulse, comprising: a base wave, twosources of different signal energy, means for shaping said base wave toproduce two base pulse waves, one of which has pulses with a slopingleading edge and the other of which has pulses with a sloping trailingedge, said base pulse waves being out of phase with each other, means tomodulate said two pulse waves respectively in time modulation withenergy from said signal sources, and a mixing means to combine saidpulse waves into a single pulse wave wherein adjacent pulses, one fromeach pulse wave, form a single pulse thereof.

5. The system of claim 4 wherein said means to produce said base pulsewave having a sloping trailing edge includes means to delay the basewave and means to differentiate and clip the resulting delayed basewave.

6. The system of claim 4 wherein said means for producing the two pulsetrains includes means to produce a base wave having a sloping edge andmeans to clip said base waveV along said sloping edge at'various levelscorresponding to the energy from said signal sources.

DONALD D. GRIEG.

REFERENCES CITED The following references are of vrecord in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,086,918 Luck July 13, 19372,391,776 Fredendall Dec. 25, 1945 2,406,790 Beatty et al Sept. 3, 19462,418,116 Grieg Apr. 1, 1947 2,434,894 Ambrose Jan. 27, 1948 2,434,965Shepard Jan. 27, 1948

